Verify toast/backend-diagnostic dedup pairing on Mars

Follow-on to MARS-461 (closed, rollup views shipped b0db7cc/v2.26.6) — verify whether Mars needs the same dedup rule Venus found (bs-mrlqhi9hhir): Venus's backend-diagnostic categories (crearPracticaFailed etc.) always co-occur with a toast/error-shown row ~0.3-0.5s later for the same user event, so a naive opt-out criteria double-counts one user friction event as two rows. Mars check: does appEvents category='practica' action IN (create-rejected, edit-rejected, self-delete-rejected) — already in vFrictionEvents's current allowlist, structurally the same 'backend diagnostic' shape as Venus's pattern — co-occur with a category='toast' row for the same actorUserId within ~0-1s? JOIN on actorUserId + close createdAt, not absence-grep. If yes: same dedup-exclude-the-diagnostic-keep-the-toast rule needed in Mars's future opt-out criteria (feeds the still-open 3-way mars/pluto/venus criteria convergence). If no: Mars's WHERE clause just differs on that one clause, report back either way.